Market Data

Market data is available on the dedicated KalshiMD session. It supports order book snapshots and incremental updates for margin markets. Subscriptions are identified by Symbol<55>. KalshiMD does not support message retransmission. Use ResetSeqNumFlag<141>=Y on Logon.

Message Flow

Market Data Request (35=V)

Tag	Name	Type	Required	Description
263	SubscriptionRequestType	Char	Y	`0`=Snapshot, `1`=Snapshot plus updates, `2`=Disable previous snapshot plus update request
146	NoRelatedSym	Integer	C	Number of `55=Symbol` entries in the repeating group that follows. Required for `263=0` and `263=1`. For `263=2`, the listed symbols are unsubscribed; omit to cancel all of the session’s subscriptions.
55	Symbol	String	C	Repeating group field. The margin market tickers to subscribe to or cancel.

Example snapshot request

8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=0|146=1|55=BTC-PERP|

Example snapshot-plus-updates subscription

8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=1|146=1|55=BTC-PERP|

Example cancel a symbol

8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=2|146=1|55=BTC-PERP|

Example cancel all subscriptions

8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=2|

Market Data Snapshot Full Refresh (35=W)

Sent in response to a snapshot request and immediately after a snapshot-plus-updates subscription is accepted. Correlate by Symbol<55>.

Tag	Name	Type	Required	Description
55	Symbol	String	Y	Margin market ticker.
268	NoMDEntries	Integer	Y	Number of book levels.
269	MDEntryType	Char	Y	Repeating group field. `0`=Bid, `1`=Offer
270	MDEntryPx	Price	Y	Book level price in dollars.
271	MDEntrySize	Quantity	Y	Book level size in contracts.

Example snapshot response

8=FIXT.1.1|35=W|49=KalshiMD|56=your-api-key|55=BTC-PERP|268=2|269=0|270=19.5000|271=10.00|269=1|270=19.5100|271=5.00|

Market Data Incremental Refresh (35=X)

Sent after a subscribed market’s aggregated book levels change or a trade occurs. Correlate by Symbol<55> on each entry.

Tag	Name	Type	Required	Description
268	NoMDEntries	Integer	Y	Number of market data entries.
279	MDUpdateAction	Char	Y	Repeating group field. `0`=New, `1`=Change, `2`=Delete.
55	Symbol	String	Y	Repeating group field. Margin market ticker.
269	MDEntryType	Char	Y	Repeating group field. `0`=Bid, `1`=Offer, `2`=Trade
270	MDEntryPx	Price	Y	Price in dollars.
271	MDEntrySize	Quantity	Y	Size in contracts.
2446	AggressorSide	Char	C	Trade entries only. `1`=Buy, `2`=Sell.

Example incremental update

8=FIXT.1.1|35=X|49=KalshiMD|56=your-api-key|268=1|279=1|55=BTC-PERP|269=0|270=19.5000|271=15.00|

Example trade update

8=FIXT.1.1|35=X|49=KalshiMD|56=your-api-key|268=1|279=0|55=BTC-PERP|269=2|270=19.5000|271=3.00|2446=1|

Market Data Request Reject (35=Y)

Sent when a market data request cannot be accepted. Unknown market tickers are not currently rejected; the server sends an empty snapshot if it has no order book for the requested symbol.

Tag	Name	Type	Required	Description
281	MDReqRejReason	Char	N	Reject reason.
58	Text	String	N	Human-readable rejection detail.

Common Reject Reasons (281)

2=Insufficient bandwidth, including request or session symbol limits
4=Unsupported SubscriptionRequestType

Overview

REST

WebSockets

FIX

Message Flow

Market Data Request (35=V)

Market Data Snapshot Full Refresh (35=W)

Market Data Incremental Refresh (35=X)

Market Data Request Reject (35=Y)

Common Reject Reasons (281)

​Message Flow

​Market Data Request (35=V)

​Market Data Snapshot Full Refresh (35=W)

​Market Data Incremental Refresh (35=X)

​Market Data Request Reject (35=Y)

​Common Reject Reasons (281)

Message Flow

Market Data Request (35=V)

Market Data Snapshot Full Refresh (35=W)

Market Data Incremental Refresh (35=X)

Market Data Request Reject (35=Y)

Common Reject Reasons (281)